Georgia Arms has a really good rep, and good prices for reloaded ammo. Ammunition in all shapes and sizes too. I just bought a bunch of ammo (check out their "Canned Heat") at a local gun show. Haven't fired it yet, but it looks well made. Going out for a range test tomorrow!
+1 for Georgia Arms. I use their Canned Heat 9mm, .38, and .45 for the range, and it's always been great. I'm not sure if they sell .357 magnum in the bulk "Canned Heat" though.
Very hard to find an online source for practice ammo that can beat Walmart. Georgia Arms doesn't sell canned heat in .357 mag but their regular stuff is a good deal and can be had in quantity. .357 Magnum 158gr Plated Semi-Wadcutter 100pk